(1) Field of the Invention
The present invention generally relates to a method and apparatus for locating artery stenoses in blood vessels. More particularly, the present invention is directed to the use of array sensor technology to determine the location of artery stenoses in animals and human beings.
(2) Description of Prior Art
There have previously been known several methods in the art for detecting artery disease, including the most traditional method, which relies upon the ability of a practitioner to detect the existence of artery stenoses with a stethoscope. Other recently known methods include the use of microphones, amplifiers, and recording oscillographs.
However, none of the known methods accurately and efficiently determine the location of the blockage within the artery, nor do the known methods provide for analysis of a detected and localized artery stenosis in humans and animals. Accordingly, the currently known methods are not completely effective for early stage diagnosis of artery disease. Further, the known methods for locating artery stenoses in blood vessels are unable to effectively eliminate background noises including heartbeat, pulse and breathing, which will interfere with the detection of the blockage in the blood vessel.
One specifically known method and apparatus for the detection and recordation of high frequency sound in the cardiovascular system is found in U.S. Pat. No. 3,762,397 to Cage. This apparatus, however, utilizes only a single microphone placed on the surface of the skin instead of an array of motion sensors, and is therefore unable to effectively increase the signal to noise ratio of the signals emitted from the noise source.
Another method which utilizes a microphone for detection of sound is disclosed in U.S. Pat. No. 3,773,033 to Robard et al. In addition to the microphone, an arterial vibration sensor is utilized. Neither of the microphone nor the sensor, however, is utilized in an array.
U.S. Pat. No. 4,989,611 to Zanetti et al. discloses a cardiac compression wave measuring system and method. Although a sensor is utilized, it is only known to provide a single sensor as opposed to an array of sensors. Further, only compression waves are detected and measured whereas the invention described in accordance with the present application utilizes an array of sensors which measure all wave energy, including but not limited to compression waves.
Another non-invasive diagnostic system for coronary artery disease is disclosed in U.S. Pat. No. 5,109,863 to Semmlow et al. and utilizes an acoustic transducer. The sensor, however, is a single sensor and is not intended to function as an array.
Each of U.S. Pat. Nos. 5,170,796 to Kobayashi and U.S. Pat. No. 5,293,874 to Takahashi et al. are directed to the detection and measurement of pulse waves. The focus of these patents is on pulse waves and does not include detection of all wave energy in the human body. With regard to Kobayashi, only pressure sensors are used to the exclusion of motion and strain sensors, as are disclosed in the instant application. Additionally, Kobayashi requires that each pressure sensing element is smaller than the lumen in the blood vessel and further that the pressure sensing elements cross over the radial artery substantially perpendicular to the direction of extension of the artery. Such a requirement presumes exact knowledge of the location of the artery as well as the orientation of the sensors with respect to the artery, thus excluding the possibility of detection at some part of the body including a blood vessel which is not near the skin surface. Further, the sensors of Kobayashi are plural in number in order to generate a scan sequence in order to provide a reference distribution whereas the present invention utilizes the array to improve the signal to background noise ratio to detect desired signals.
In Takahashi, the sensors for pulse wave detection are not used as an array but are instead positioned at upstream and downstream sides of a blood flow for measuring a transmission velocity of a pulse wave.